Process of making powdered metal article



New. 23, 1954 J. HALLER PROCESS OF MAKING POWDERED METAL ARTICLES 2 Sheets-Sheet l ll/IA Filed Jan. 10, 1949 Fig.5.

Nov. 23, 11954 J. HALLER 2,695,230

PROCESS OF MAKING POWDERED MEZTAL'ARTICLES Filed Jan. 10, 1949 2 Sheets-Sheet 2 Z'mnentor (lttornegs United States Patent PROCESS OF MAKING POWDERED METAL ARTICLE John Haller, Detroit, Mich., assignor to Michigan Powdered Metal Products Co., Inc., Northville, Mich., a corporation of Michigan Application January 10, 1949, Serial No. 70,056

9 Claims. (Cl. 75-208) This invention relates to processes of making powdered metal articles.

One object of this invention is to provide a process of making hollow or bored powdered metal articles without the necessity of providing a removable core or even a core capable of removal, the core itself being self-removing and completely disappearing, even though the cavity or bore is entirely surrounded by the walls of the article.

Another object is to provide a process of making a powdered metal article wherein a core of infiltratable ma terial is inserted in the die cavity, surrounded by the powdered metal, which is then pressed into the desired form, after which the pressed article is sintered at a high temperature, during which the core material infiltrates the pores of the powdered metal article and leaves a hollow in the article corresponding in configuration to the previous configuration of the core.

Another object is to provide a process of making a powdered metal article as set forth in the object immediately preceding, wherein an infiltratable core material of such character is provided that it not only disappears within the body of the metal itself, leaving a cavity of corresponding configuration where it previously rested, but also enhances the hardness and, if desired, the tensile strength of the article over what it would have been without the presence of the infiltratable material.

In the drawings:

Figure l is a side perspective view. partly in central vertical section, of a powdered metal article with an internal cavity formed according to the present invention;

Figures 2 to 6 inclusive are diagrammatic views showing successive stages in the process of producing the powdered metal article shown in Figure 1;

Figure 7 is a side perspective view of the core of infiltratable material used in producing the hollow powdered metal article shown in Figure 1, according to the process of Figures 2 to 6 inclusive;

Figure 8 is a central vertical section through a modified article produced by the process of the present invention;

Figure 9 is a horizontal section taken along the line 9-9 in Figure 8;

Figure 10 is a side elevation of a further modification:

Figure ll is a bottom plan view of the article shown in Figure 10;

Figure 12 is a side elevation of a further modified article produced according to the process of the present invention;

Figure 13 is a side elevation of the article shown in Fi ure 12, taken at right angles thereto; and

Figure 14 is a central vertical section through a still further modified article produced according to the process of the present invention.

In general. the process of the present invention consists in imbedding a core of infiltratable material within a mass of powdered metal in a die cavity. pressing the powdered metal into the desired form, and sintering the pressed article at a temperature in the neighborhood of 2000 F. During the sintering operation, the core dis a pears into the pores of the powdered metal by infiltration through the action of capillary attraction. leaving a cavity, indentation or other alteration of configuration corresponding to the shape previously possessed by the infiltratable core. The core may be an alloy of copper and zinc, which it has been found will infiltrate readilv into a powdered iron article at a sintering temperature Patented Nov. 23, 1954 in the neighborhood of 2000 F. It has been found that cavities, indentations or bores of the most intricate shape can be produced cheaply and easily by this process and that the powdered metal article resulting from the process has an increased hardness and tensile strength over articles which have not been infiltrated.

In particular, with articles made of powdered iron, it has been found that an alloy of per cent copper and 15 per cent zinc infiltrates well and produces an article of increased hardness and tensile strength. This may be used either in the form of an alloy core, or i the form of a sintered core of powdered copper and zmc.

Let it be assumed, for example, that the powdered metal article 10 shown in Figure 1 is to be produced. It consists of a cylindrical metal body 11 having an annular cavity 12 in its interior, the outer wall 13 of the cavity being threaded. Such an article is virtually incapable of production by ordinary methods of casting and molding, but is easily made by the present process.

To produce the annular cavity 12, a core 14 is formed of tubular shape and having a central bore 15 corresponding to the diameter 16 of the core portion in the article 10. The outer surface 17 of the core 14 is threaded with threads corresponding to the threads 13 desired on the outer wall 18 of the cavity 12. The threads 13 may of course be omitted if it is desired to make a smooth-walled cavity.

in forming the article, a conventional molding press, generallwdesignated 20 shown diagrammatically in Figures 2 to 6 inclusive, is employed. It is shown as consisting of a die block 21 having a die cavity 22 in the form of a bore in which upper and lower plungers or punches 23 and 24 respectively move in opposite directions. For short articles, a single plunger may be used but for elongated articles, two oppositely-moving plungers are preferred. The plungers 23 and 24 are moved toward one another in a predetermined cycle and in timed relationship in accordance with a desired cycle. The plungers 23 and 24 may be reciprocated either mechanically or by means of pressure fluid in any suitable press. The details of the press form no part of the present invention and any suitable conventional press may be employed, together with the use either of hand charging or a charging device for inserting the powder in the mold. Such a press and charging device are disclosed and claimed in my co-pending application Serial No. 780,851 filed October 20, 1947 for Briquetting Machine now Patent No. 2,608,826.

In carrying out the process to produce the article 10 shown in Figure l, the plungers 23 and 24 are retracted to the positions shown in Figure 2. A quantity of metal powder such as iron powder I is then placed in the die cavity 22 above the lower plunger 24 with its top surface at the estimated height above its bottom surface that the lower end of the cavity 12 is expected to occupy, making due allowance for diminution in size due to compression. The ordinary reduction in size, that is the ratio of the space occupied by the powdered metal to the space occupied by the solid product pressed from it. is between 2.5 to 1 and 3 to 1, hence the preliminary filling of the die cavity 22 must take this factor into account.

When the partial filling has been completed to the desired level described above, the infiltratable core 14 is placed in position on top of the iron powder I (Figure 3) and in the desired location laterally. The space around the core 14 is then filled up with the iron powder I to the desired level (Figure 4), again taking into account the reduction in size due to compression within the die cavity 22. Instead of partially filling the die cavity 22, the core 14 may be grasped and held in position at the desired level and location within the die cavity 22 by a suitable fixture supported on or from the upper surface 25 of the die block 21 while filling is accomplished, the fixture being removed when the powder has risen sufficiently far enough to securely locate the core 14 without danger of displacement.

The mechanism of the press 20 is then operated so as to advance the two plungers 23 and 24 toward one another (Figure 5), compressing the iron powder I between them with a sufiicient pressure to obtain the desired degree of porosity or density for the finished article and to force the iron powder into the various recesses of the core 14, for example, a pressure of 25 to 30 tons for small articles. The upper plunger 23 is then retracted and the lower plunger 24 advanced (Figure 6) until the article 10 is raised to the level of the top surface of the die block 21, thereby ejecting the article 10 containing the core 14 in its interior.

The green or unsintered article 10 is then placed 1n a sintering oven and subjected to a suitable sintering temperature, the amount of which, and the time of sintering are varied to suit the particular piece. For a small article, such as that shown in Figure 1, a sintering for onehalf an hour at 2020 F. has been found satisfactory. If the sintering time or temperature are made too long or too high respectively, an undesirable grain structure is set up in the metal. The sintered article is then cooled under atmospheric-controlled conditions down to room temperature, when it is removed as a finished piece.

If the article is now split or sawed in two, it is found that a cavity has been formed in its interior corresponding substantially exactly to the configuration of the core 14. The core 14 itself has left no trace, provided it was not of too large volume to be absorbed by the powdered iron, and has disappeared into the pores of the iron. The core 14, in thus infiltrating the pores of the iron, is found to increase the hardness and tensile strength of the iron, so

that a stronger and more durable article is obtained in comparison with an uninfiltrated iron article. In the finished article 10, furthermore, it is found that the threads on the outer surface 17 have reproduced themselves almost exactly in the threaded outer wall 18 of the article 10.

From the foregoing description, it will be evident that the volume of the core 14 must not be greater than the percentage of porosity of the powdered iron or other article 10 produced, otherwise the core will leave a remnant or residue known as a sinter plug. If desired, a hollow core can be employed to compensate for an excessive volume occupied by the core itself, enabling a large core to be absorbed without leaving a residue. Such a hollow core must, of course, be of sufficient strength to withstand the pressing force. During the pressing operation within the press 20, the core 14 of course moves a proportionate distance corresponding to the amount of compression imparted to the article 10 itself.

The modified articles to 33 inclusive shown in Figures 8 to 14 inclusive are merely variations of a wide variety of articles which may be produced by the present process. The article 30. for example, has an enlarged cavity 34 in the interior thereof, communicating with the exterior by a reduced diameter bore 35. The cavity 34 may also have ribs or lands 36 or grooves 37 (Figure 9) as desired. The core is merely provided with indentations corresponding to the ribs 36 and projections corresponding to the grooves 37. The core for the article 30, as well as for the articles 10. 31, 32 and 33 may itself be formed by powdered metallurgv procedures in order to produce it quickly and cheaply in large quantities.

The article 31 consists of a cylindrical body 40 having a flanged head 41 on one end thereof and havin an inclined or spiral cam groove 42 around the periphery of the cylindrical portion or barrel 40. A bore 43 accommodates a shaft (not shown). The inclined or spiral cam groove 42 is formed by the use of an arcuate insert of infiltratable powdered metal placed adjacent the wall of the die cavity 22 in an inclined or spiral position. When pressing has been accomplished and the green or unsintered article 31 ejected from the mold. the core is found embedded in the outer wall of the barrel portion 40. Upon sintering the article 31 in the previously-described manner, the core disappears into the pores of the iron or other metal constituting the barrel 40, leaving the cam groove 42 perfectly formed and of the desired configuration and location.

The article 32 is an example of a body 44 having a flange 45 on one end, sockets 46 and 47 in its opposite ends, an annular groove 48 around its midportion, and a bore 49 of square cross-section passing through it from one side to the other. The groove 48 and bore 49 are easily made by means of cores of infiltratable metal in the manner described above, the sockets 46 and 4 e g preferably formed by pressing, although also capable of being formed by the use of an infiltratable core.

The article 33 illustrates the formation of an enlarged internal cavity 50 within a cylindrical block 51 if iron or other inflltratable metal, lateral bores 52 extending sidewise and oblique bores 53 radiating upward to a circular recess 54 in the top of the article. A bore 55 leads from the cavity 50 to the lower end of the article. In this manner, a spider 56 is formed at the upper end of the article, separated from the remainder of the body 51 by the passageways or bores 53.

In surface infiltration, to produce surface recesses or grooves, such as the cam groove 42 in the article 31 (Figures 10 and 11), or the annular groove 48 (Figures 12 and 13), care must be taken to avoid the formation of a surface oxidation on the copper alloy insert, as this tends to retard or prevent the release of all of the copper by infiltration. By the present process, recesses or cavities of great intricacy can be produced in an article of any desired form which is moldable. The process, for example, may be used to produce cylinders with passageways, valves with valve ports, spray nozzles with orifices or wheels or other rotary parts with internal gears, ratchet teeth, splines, internal cam grooves, threads, bosses, spiders or other shapes in an obvious manner by the use of a properly configured core or insert of infiltratable material. If powdered iron is used as the material for the article, carbon may be incorporated in it to raise its tensile strength and to enable it to be heattreated or case-hardened. It may, for example, be carburized by the use of a carburizing gas and is preferably quenched immediately to avoid disapearance of the carbon. Side core holes with radial, axial or skew directions and of any cross-section, may easily be produced.

What I claim is:

1. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal, said insert being formed of metal infiltratable into the bores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insert-containing body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and effecting infiltration of substantially all of said insert metal into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

2. A process of internally infiltrating a powdered metal 7 article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal, said insert being formed of metal alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insert-containing body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and effecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

3. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal, said insert being formed of copperzinc alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insertcontaining body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and effecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

4. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal, said insert being formed of copperzinc-lead alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insertcontaining body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and effecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

5. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal consisting predominantly of powdered iron, said insert being formed of metal alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insert-containing body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and effecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

6. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal consisting predominantly of powdered iron, said insert being formed of copper-zinc alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insert-containing body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and effecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

7. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said proces comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal consisting predominantly of powdered iron, said insert being formed of copper-zinc-lead alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insert-containing body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal and efiecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

8. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding said insert in a mass of powdered metal consisting predominantly of powdered iron, said insert being formed of copper-zinc alloy infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insert-containing body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal at a temperature in the neighborhood of 2000 Fahrenheit and effecting infiltration of substantially all of said insert alloy into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

9. A process of internally infiltrating a powdered metal article with a strengthening metal without producing surface erosion of said article and simultaneously forming an internal cavity of predetermined shape therein, said process comprising forming an insert of predetermined shape and dimensions, embedding and completely covering said insert in a mass of powdered metal consisting predominantly of powdered iron and carbon, said insert being formed of metal infiltratable into the pores of said powdered metal, the shape and dimensions of said insert corresponding to the shape and dimensions desired for said cavity, compressing the mass of metal containing the insert into a body of desired shape, sintering the insertcontaining body at a sintering temperature above the melting point of said insert and below the melting point of said powdered metal to effect infiltration of said insert metal into said body whereby to leave a cavity in said body corresponding in shape and dimensions to the original shape and dimensions of said insert.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,051,814 Lowendahl Jan. 28, 1913 2,180,988 Lemmers et al. Nov. 21, 1939 2,227,308 Hildabolt Dec. 31, 1940 2,273,589 Feb. 17, 1942 2,341,860 Ellis Feb. 15, 1944 2,363,337 Kelly Nov. 21, 1944 2,373,405 Lowit Apr. 10, 1945 2,402,120 Boegehold June 18, 1946 2,408,430 Lowey Oct. 1, 1946 2,413,512 Morin Dec. 31, 1946 2,422,439 Schwarzkopf June 17, 1947 2,456,779 Goetzel Dec. 21, 1948 2,462,045 Wulff Feb. 15, 1949 2,561,579 Lenel July 24, 1951 FOREIGN PATENTS Number Country Date 138,424 Australia Sept. 10, 1947 452,503 Great Britain Aug. 17, 1936 573,740 Great Britain Dec. 4, 1945 611,466 Great Britain Oct. 29, 1948 OTHER REFERENCES Abridgement published September 7, 1950, in the Official Journal of Patents, Trade-Marks and Designs, on page 2611, vol. 20, Number 33. 

1. A PROCESS OF INTERNALLY INFILTRATING A POWDERED METAL ARTICLE WITH A STRENGTHENING METAL WITHOUT PRODUCING SURFACE EROSION OF SAID ARTICLE AND SIMULTANEOUSLY FORMING AN INTERNAL CAVITY OF PREDETRMINED SHAPE THEREIN, SAID PROCESS COMPRISING FORMING AN INSERT OF PREDETERMINED SHAPE AND DIMENSIONS, EMBEDDING SAID INSERT IN A MASS OF POWDERED METAL, SAID INERT BEING FORMED OF METAL INFILTRATABLE INTO THE BORES OF SAID POWDERED METAL, THE SHAPE AND DIMENSIONS OF SAID INSERT CORRESPONDING TO THE SHAPE AND DIMENSIONS DESIRED FOR SAID CAVITY, COMPRESSING THE MASS OF METAL CONTAINING THE INSERT INTO A BODY OF DESIRED SHAPE, SINTERING THE INSERT-CONTAINING BODY AT A SINTERING TEMPERATURE ABOVE THE MELTING POINT OF SAID INERT AND BELOW THE MELTING POINT OF SAID POWDERED METAL AND EFFECTING INFILTRATION OF SUBSTANTIALLY ALL OF SAID INSERT METAL INTO SAID BODY WHEREBY TO LEAVE A CAVITY IN SAID BODY CORRESPONDING IN SHAPE AND DIMENSIONS TO THE ORIGINAL SHAPE AND DIMENSIONS OF SAID INSERT. 